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Abstract: Poly(hydroxyalkanoate)s (PHAs) have attracted much attention as environmentally compatible polymeric materials that can be produced from renewable carbon resources. Biodegradation of PHA materials occurs by the function of extracellular [...]

The interaction between denatured poly[(R)-3-hydroxybutyrte] (dPHB) depolymerase and the dPHB surface is investigated by a combination of PCR random mutagenesis targeted only to the substrate-binding domain (SBD) region and an in vivo screening system to identify the amino acid residues relating to dPHB adsorption. The kinetic analysis of the dPHB degradation suggested that lowering the affinity of the SBD towards dPHB causes a decrease in the dPHB degradation rate without the loss of its hydrolytic activity for the polymer chain.

Polyhydroxyalkanoates (PHAs) are polyesters of 3-hydroxy alkanoic acids that are produced as intracellular granules by different bacteria. A study was conducted to prove that short0chain-length (SCL) medium-chain-length (MCL) PHAs can be made from glucose in recombinant E. coli.

Research has been conducted on the phasins, polyhydroxyalkanoate granule-associated proteins. Results indicate that these phasins interact with polyhydroxyalkanoate via direct binding.

Researchers used PCR-mediated random mutagenesis of the gene for polyhydroxyalkanoate (PHA) synthase in Aeromonas caviae to generate two versions of the enzyme that exhibited 21% and 56% increased activity toward 3-hydroxybutyrate-coenzyme A. This caused a 6.5-fold increase in the production of a PHA copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate.

The cloning of polyhydroxybutyrate depolymerase gene (phaZ(sub Pst)) of Pseudomonas stutzeri and the functional analysis of the substrate-binding domains have been undertaken. It was discovered that phaZ(sub Pst) is made up of 1,728 bp encoding a protein of 576 amino acids. The protein has a domain structure with a catalytic domain, a putative linker region and two putative substrate-binding domains.

Two kinds of polyhydroxyalkanoate (PHA) biosynthesis gene loci (phb and pha) of Pseudomonas sp. strain 61-3, which forms a blend of poly(3-hydroxybutyrate) (P(3HB)) homopolymer and a random copolymer, were cloned and studied at the molecular level. Findings showed that PHB synthase and two PHA synthases of Pseudomonas sp. strain 61-3 are specific for short chain length and both short and medium chain length 3-hydroxyalkanoate units, respectively.

Research was conducted to examine the cloning and characterization of the polyhydroxyalkanoate (PHA) synthase gene of Comamonas acidovorans, DS-17. Substrate specificity of C acidovorans was analyzed using as heterologous hybridization probe the synthase gene of Alcaligenes eutrophus. Results indicate that the monomer-supplying pathway plays a significant role in determining the type of PHA that can be produced.

An experiment is conducted to provide direct evidence that ORF3 is important for polyhydroxyalkanoate (PHA) biosynthesis from alkanoic acids in Aeromonas caviae. Complementation analysis involving the PHA-negative mutant of the bacteria revealed the role of ORF3 in the biosynthesis of alkanoic acids. The (R) specific hydration of 2-enoyl-CoA is identified as a channeling pathway for providing (R)-3-hydroxylacyl-Coa monomer units to poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) biosynthesis.

A research was conducted to study the purification of the extracellular polyhydroxybutyrate (PHB) depolymerase from the culture supernatant of Comamonas acidovorans and to examine its biochemical and kinetic properties. The function of the putative substrate-binding domain was determined through a fusion protein with glutathione S-transferase formed in Escherichia coli. Results indicated that the PHB depolymerase was composed of discrete domains connected by a linker region.

The EcoRV-EcoRI restriction fragment was cloned and analyzed from genomic DNA of aeromonas cavia, a bacteria. The cloned fragments complemented PHA-negative mutants of alcalignes eutrophus and pseudomonas putida, and were able to synthesize P(3HB-co-3HHX). There was (R)-enoyl-coenzyme A hydratase activity in escherichia coli expressing ORF3.